At FeedBurner, under Optimize, fill in all the Smartcast stuff. Keep descriptions short and make your point in the first few words – that’s what people see in the Description field in iTunes. Avoid abbreviations! – no matter what you try it will look like “& nbsp” either in your feed or iTunes.

Take the time in Feedburner>>Optimize>>FeedFlare to give your listeners/readers as many options as make sense for subscribing: subscribe by email, use Add to Any, etc. Think of this feedburner feed as your secondary feed – as of now, WP does not allow you to replace it’s feed with it, so offer it alongside.